Patent Document 1 discloses an operation device including a rotating body rotationally operated by a user, a supporting body supporting the rotating body in a rotatable manner, and a detection device detecting a rotationally operated position (rotational angle) of the rotating body. The detection device detects a capacitance generated between a user's fingertip placed at a predetermined position of the rotating body and an electrode attached to the supporting body and detects a rotationally operated position of the rotating body on the basis of the detection result.